Equol is an isoflavan compound having a structure represented by Formula 1, and is produced through conversion of isoflavonoids in foods by intestinal fauna in response to consumption of beans.

It is reported that equol, which is an active metabolite of soybean isoflavone, has the key role in the efficacy of soybean foods in clinical applications. Namely, much research have shown that equol, which is a metabolite of soybean isoflavone, is more effective to breast cancer, prostate cancer, anti-aging, menopausal disorder and postmenopausal osteoporosis than soybean isoflavone (See. [D. Ingram, et al., (1997) Lancet, 350, 990-994]; [A. M. Duncan, et al., (2000) Cancer Epidemiology, Biomarkers & Prevention, 9, 581-586]; [C. Atkinson, et al., (2002) J. Nutr., 32(3), 595S]; [H. Akaza, et al., (2002) Jpn. J. Clin. Oncol., 32(8), 296-300]; [S. Uchiyama, et al., (2001) Ann Nutr. Metab., 45, 113(abs); Biol Reprod. 2004; 70: 1188-95], and the like).
It is also reported that equol is produced by intestinal bacteria, and the production of equol differs depending on the ability of an individual to produce equol [see: Nutr Cancer. 2000; 36:27-32]. It is estimated that a person who is unable to produce equol does not have bacteria capable of producing equol in the intestine. In such a case, it is thought that such a person cannot expect desired anti-estrogen effects or estrogen-like effects even if soybean processed foods are consumed by the person. In order to achieve desired effects, a person may intake live bacteria capable of producing equol or equol itself.
On the other hand, although production of such a useful equol can be attempted through bioengineering synthesis, there are some technical problems to be overcome due to the fact that the production of equol consists of complex biochemical pathways requiring various microorganisms (see FIG. 2), and that equol-producing microorganisms have very slow growth and reaction rates, like most anaerobic microorganisms.
Accordingly, for the purpose of more practical research, many studies have focused on the investigation of intestinal bacteria capable of producing equol or materials capable of promoting equol production. Bacteroides ovatus, Streptococcus intermedius, and Streptococcus constellatus are reported as microorganisms having equol production capability (International Patent Application Publication 1999/07392). Furthermore, through various prior investigations, it has been reported that various monosaccharides or polysaccharides have excellent ability to increase or decrease equol concentration. Specifically, saccharides such as adonitol, arabinose, erythritol, galactose, lactitol, melezitose, trehalose, ribose, sorbose, xylose, inositol and solbitol and the like contribute to increased equol concentration (see: Table 1 below in International Patent Application Publication 2007/052749).
TABLE 1Equol concentrationActivity toin mediumregulate equolSaccharide(μM)concentration (%)Adonitol47.0260.0Arabinose70.6391.1Cellobiose29.0160.6Erythritol38.7214.2Fructo-oligo0.00.0saccharidesFructose9.351.5Galactose65.0240.1Glucose0.00.0Glycogen33.4184.8Inulin0.00.0Lactitol82.9459.1Lactose0.00.0Lactulose1.58.1Inositol75.2416.2Maltose10.658.5Mannitol32.9182.2Mannose15.083.0Melezitose74.3411.6Melibiose4.524.8Raffinose0.00.0Rhamnose21.0116.4Ribose59.5329.6Sorbiol67.3372.5Sorbose84.5467.7Sucrose0.00.0Galacto-0.00.0oligosaccharidesTrehalose72.9403.5Xylose79.9442.6Saccharide no add18.1100.0
Psicose is a monosaccharide having sweetness similar to that of sugar and ultra low calories, and thus is widely used as a functional sweetener. Specifically, psicose is classified as a keto-hexose, which is a rare sugar found in trace amounts in nature. It has been reported that psicose is produced from fructose by D-tagatose 3-epimerase. The intensity and sweetness of psicose are very similar to those of fructose. However, unlike fructose, because psicose is almost not metabolized when psicose is consumed in the body, psicose has almost zero-calories, and inhibits enzyme activity relating to lipid synthesis, thereby reducing abdominal obesity. In this regard, psicose may be used as an effective ingredient for diet foods. Furthermore, sugar alcohols, which are widely used as sugar substitutes, have side effects such as diarrhea when consumed in certain amounts, while psicose has substantially no side effects (see Matsue, T., Y. Baba, M. Hashiguchi, K. Takeshita, K. Izumori, and H. Suzuki. 2001. Dietary D-psicose, a C-3 epimer of D-fructose, suppresses the activity of hepatic lipogenic enzymes in rats. Asia Pac. J. Clin. Nutr. 10:233-237; Matsuo, T., and K. Izumori. 2004. D-psicose, a rare sugar that provides no energy and additionally beneficial effects for clinical nutrition. Asia Pac. J. Clin. Nutr. 13:S127).
The present inventors set out to investigate functional foods having a capability to accelerate equol conversion, besides general sugars and polysaccharides reported until now. As a result of continuous efforts, it has been found that psicose known as a functional sweetener exceptionally promotes the production of equol. Based on the results, the present invention has been accomplished.
In order to evaluate relative comparison of equol conversion efficacy of various saccharides, materials showing high conversion promoting rate were primarily selected based on the literature. Representative materials having excellent equol conversion promoting rate selected based on the literature may include lactitol, inositol, melezitose, sorbose, trehalose, and xylose.
Further, the present inventors focused on general, naturally occurring saccharides rather than sugar alcohols, and selected xylose as a representative comparison material. In order to minimize difference in experimental method and incorrectness on experimental errors, the present inventors defined saccharides exhibiting relatively high conversion rate than xylose as test materials having an effect of promoting equol conversion rate. The present inventors performed a series of experiments on novel general (functional) saccharides, which did not satisfy the purpose, and obtained a significant result that psicose promotes equol production. Based on such results, the present invention has been accomplished.
The present invention relates to an equol level regulator including psicose as an effective ingredient. More specifically, the present invention relates to an equol level regulator including psicose as an effective ingredient to accelerate equol production by human intestinal fauna.